The present invention relates generally to energy measurement and more specifically the invention pertains to a type of electrostatic energy analyzer for charged particles (electrons and ions).
The simplest device for analyzing the energies of a group of charged particles is the planar retarding potential analyzer (RPA), consisting of an electrically biased screen placed between two electrically biased screens. Although simple, such an analyzer suffers from the drawback that it accurately determines the energies of particles only if they are moving along a line perpendicular to the grids. If the particles enter off-axis, errors are introduced into the measurement. In practical terms, to get good energy resolution from a planar RPA, it is necessary to use fine mesh screens, which limits the amount that the size of the analyzer can be reduced.